With the popularity of smartphones and rapid development of high-speed mobile Internet technologies, communications systems, such as International Mobile Telecommunications 2000 (3G), a Worldwide Interoperability for Microwave Access system (WiMAX for short), a Long Term Evolution system (LTE for short), and a Long Term Evolution Advanced system (LTE-A for short), which are involved in various wireless broadband access technologies, keep emerging. In the foregoing wireless communications system, on same time and frequency resources, data can only be received or sent between a base station and user equipment, but data cannot be received and sent simultaneously between a base station and user equipment. For example, in a Frequency Division Duplex (FDD for short) system, a base station sends data to a user and receives data from the user separately by using different frequency resources; and in a Time Division Duplex (TDD for short) system, a base station sends data to a user and receives data from the user separately by using different time resources.
In evolution of the wireless broadband access technologies, in a case of considering neither a higher-order modulation technology nor configuration of more transmit and receive antennas, usually, a greater communication bandwidth is used to obtain a higher peak rate, for example, an LTE system supports a maximum system bandwidth of 20 MHz, while an LTE-A system can support a maximum system bandwidth of 100 MHz by using a carrier aggregation technology. However, wireless spectrum resources are very rare and expensive, causing that the limited spectrum resources become a barrier to further improvement of a system capacity.
To improve a utilization rate of spectrum resources, a new full-duplex communications technology is proposed. A specific technical means is used to reduce interference caused when a communications device receives and transmits signals simultaneously, so that the communications device can implement bidirectional transmission of communication data, where the communications device includes a base station, user equipment (UE for short), and the like, and the technical means may be at least one of the following: antennas are appropriately arranged on a device to enable signals from multiple transmit antennas to just cancel out each other at a receive antenna, or a known signal transmitted by a transmit circuit is used in a receive circuit to perform interference cancellation. Notably, the new full-duplex communication herein refers to that: a base station and UE can perform bidirectional data transmission on a same time-frequency resource. For example, in an LTE system, if a base station is full-duplex, two UEs that are sufficiently far away from each other and that are managed by the eNB can receive and transmit data and/or signaling on a same time-frequency resource; in this way, a spectrum utilization rate can be improved, where the base station may be an evolved NodeB, which is briefly referred to as an eNodeB or an eNB.
In an FDD system, a full-duplex eNB is used and can support transmission of uplink data and downlink data on a same carrier, for example, downlink data and uplink data are transmitted on an uplink carrier, and uplink data and downlink data are transmitted on a downlink carrier.
However, if UE managed by a full-duplex eNB also has a duplex capability, the UE does not know a carrier that transmits uplink and downlink data or signaling, and therefore, cannot effectively transmit information.